1. Department of Arctic Environment, National Environmental Research Institute, Frederiksborgvej 399, P.O. Box 358, DK-4000 Roskilde, Denmark, Department of Veterinary Pathobiology, The Royal Veterinary and Agricultural University, Bülowsvej 17, DK-1870 Frederiksberg, Denmark, Greenland Institute of Natural Resources, P.O. Box 570, DK-3900 Nuuk, Greenland, Denmark, National Wildlife Research Centre, Canadian Wildlife Service, Environment Canada, and Carleton University, Raven Road, Ottawa, Ontario K1A 0H3,...